Furnace top charging devices

ABSTRACT

An improvement in a bell and bell hopper top charging device for use with a blast furnace comprises a retaining surface that projects upwardly from a frusto-conical surface of the bell to form a pocket between the frusto-conical surface and the retaining surface. This pocket is filled with raw materials. Upon lowering the bell from the bell hopper to discharge the raw materials from the bell hopper, the raw materials flow over the retained material in the pocket and out of contact with the sealing surface of the bell. The improvement further comprises a supplemental sealing means that is mounted to the bell hopper for engagement with the sealing surface of the bell for maintaining a gastight seal between the bell and the bell hopper. The improvement also comprises a bell and a hopper that are constructed of a plurality of severable sections including two top sections and a unitary bottom section for the initial installation and two bottom sections for replacement members.

United States Patent [15] 3,679,192 [451 July 25,1972

Powell [54] FURNACE TOP CHARGING DEVICES- [72] inventor: Russell A. Powell, Pittsburgh, Pa.

[73] Assignee: Koppers Company, Inc.

[22] Filed: March 18,1970

[21] Appl. No.: 20,650

- [52] U.S. Cl. ..266/27, 214/36 [51] ..F27b 1/20 [58] Field of Search ..214/18 V, 35 R, 36, 37; 266/27 [56] References Cited UNITED STATES PATENTS 1,868,870 7/1932 Barr ..214/37 2,648,446 8/1953 Martin 3,152,703 10/1964 Slagley 3,436,063 4/1969 Woodworth et al.. 3,554,393 1/1971 Seraing 3,182,983 5/1965 Tsujihata et al. ..266/27 Primary Examiner-Gerald A. Dost Attorney-Oscar B. Brumback and-Olin E. Williams [57] ABSTRACT An improvement in a bell and bell hopper top charging device for use with a blast furnace comprises a retaining surface that projects upwardly from a frusto-conical surface of the bell to form a pocket between the frusto-conical surface and the retaining surface. This pocket is filled with raw materials. Upon lowering the bell from the bell hopper to discharge the raw materials from the bell hopper, the raw materials flow over the retained material in the pocket and out of contact with the sealing surface of the bell. The improvement further comprises a supplemental sealing means that is mounted to the bell hopper for engagement with the sealing surface of the bell for maintaining a gastight seal between the bell and the bell hopper. The improvement also comprises a bell and a hopper that are constructed of a plurality of severable sections including two top sections and a unitary bottom section for the initial installation and two bottom sections for replacement members. 1

9 Claim, 11 Drawing figures PATENTEBJMS m2 SHEET 1 OF 4 I NVEN TOR.

05.95 ,4. POWELL P'AIENTEBJMS I972 SHEET 3 BF 4 INVENTOR.

M55544 4. POWELL PNENTEB 25 I972 SHEET Q UF 4 I N VENTOR. Fl/SSELL ,4. POM 54L FURNACE TOP CHARGING DEVICES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to top charging devices for blast furnaces, and more particularly, to improvements in a blast furnace bell and bell hopper arrangement.

conventionally, a typical top charging device such as, for example, the top charging device of US. Pat. No. 3,417,982, comprising one or two chambers, is located on top of a conventional blast furnace so that blast furnace gases do not escape from the furnace as raw materials are being charged into the furnace. The charging device conventionally comprises receiving chutes, conventional flap valves, and two cooperating chambers including a small bell hopper with a cooperating small bell, and a large bell hopper with a cooperating large bell.

Skip cars, conveyors or the like carry raw materials from a loading area near the bottom of the blast furnace to the top charging device and discharge these raw materials from the skip car or conveyor through the receiving chutes, through the flap valves that have previously been opened, and then into the small bell hopper. Generally two skip loads or batches are discharged into the small bell hopper before the small bell is lowered to feed the raw materials into the large bell hopper. This procedure is repeated until an accumulation of the proper mix of ingredients is achieved in the large bell hopper. Subsequently, the large bell is lowered so that the proper mix of ingredients is discharged into the blast furnace.

Abrasion of the surfaces of bells and bell hoppers has been a long standing problem and the problem has become aggravated today where many blast furnaces are being charged with beneficiated materials that are more abrasive than heretofore known. This abrasion is accelerated by the furnaces being operated at higher pressures. Consequently, the sealing or seating surfaces of the bells and of the bell hoppers are being eroded so that it becomes increasingly difficult to maintain a tight pressure seal between the bells and the bell hoppers. This abrasion is especially severe on the sealing surfaces of the small bell hopper and the small bell, as the small bell is activated more frequently than the large bell.

2. Description of the Prior Art One approach for reducing this abrasion of bells and bell hoppers has been to dispose abrasion-resistant surfaces on the seating surfaces as well as the burden surfaces of conventional bells and bell hoppers. Herein seating surfaces refer to the surfaces of bells and bell hoppers required to form the gastight seal, and burden surfaces refer to the frusto-conical surfaces of bells and inverted frusto-conical surfaces of bell hoppers exposed to the flow of raw materials.

Heretofore small bells had two halves bolted together with these abrasion-resistant protecting surfaces applied to the burden surfaces as well as the seating surfaces. Consequently, a mechanical joint existed along these surfaces, particularly at the seating surface. This joint in the seat was conducive to gas leakage. When gas leakage occurred, abrasive solid particles, entrained in the gas, enlarged these joints of this small bell.

Heretofore, large bells have been unitary with the abrasionresistant protecting surfaces applied to both the burden as well as the seating surfaces. However, gas leakage passed between the seating surfaces of the large bell and large bell hopper to ruin the gastight seal and to develop thereafter large cavities in the burden area immediately above the seating surface.

Another approach is the use of deflecting devices for protecting the seating surface of bells and of bell hoppers. US. Pat. No. 3,182,983 shows a slidable protective shield that protects the seating surface of a conventional bell from contact with the granular materials as they are discharged from the bell hopper. A disadvantage of this protective shield is that it comprises movable parts where dust particles and the like may become entrapped between the shield and the seating surface and consequently prevent the shield from sliding, as designed.

The present invention, on the other hand, provides a simple and more reliable deflecting device as well as a novel supplemental sealing device for protecting the seating surfaces of bells and of bell hoppers. When the present invention is used with one or two compartment charging devices the service life of the bells and bell hoppers is significantly extended.

SUMMARY OF THE INVENTION In accordance with the invention, a frusto-conical bell has a retaining surface that completely surrounds and projects upwardly from the frusto-conical surface of the bell at an angle relative thereto to form a pocket for retaining raw materials.

In a preferred embodiment of the invention the retaining surface is mounted immediately above the seating surface of the bell and the retaining surface lies in a cylindrical plane that is substantially coaxial with the longitudinal axis of the bell. The height of the retaining surface from the frusto-conical surface may be varied as desired; however, its height should be sufiicient so that raw materials, when discharged from the bell hopper, flow over the retained material and out of contact with the seating surface of the bell.

The bell hopper has a novel sealing means for cooperation and engagement with the seating surface of the bell. The sealing means comprises an upper circular plate that is mounted to the lower periphery of the bell hopper immediately below its seating surface, a matching lower circular plate, a circular sealing gasket disposed between the upper and the lower plates, and fasteners for urging the upper and lower plates together. The sealing gasket, thus, has a sealing edge for engagement with the seating surface of the bell at a point below the seating surfaces of the bell and of the bell hopper whereby a gastight seal is maintained.

Moreover, the bell and the bell hopper, in accordance with the invention, are constructed of a plurality of sections including two top sections and a unitary bottom section for the initial installation and two bottom sections for replacement members.

GENERAL DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view in elevation of an embodiment of the top charging device of the invention on top of the related furnace structure;

FIG. 2 is an isolated isometric view of the small bell of FIG.

FIG. 3 is an exploded isometric view of the small bell of FIG. 2;

FIG. 4 is a cross-sectional view in elevation of the small bell of FIG. 2 taken at lines IVIV;

FIG. 5 is a cross-sectional view in elevation of the small bell cooperating with the bell hopper of FIG. 1 illustrating a preferred embodiment of the invention;

FIG. 6 is an isolated view of the lower end portion of the small bell of FIG. 2;

FIG. 7 is a cross-sectional view of the small bell taken at lines VII VII of FIG. 6;

FIG. 8 is a cross-sectional view in elevation of the small bell and of the bell hopper of FIG. 1, illustrating a method for replacing the supplemental sealing means of the bell hopper of FIG. 1;

FIG. 9 is an exploded isometric view of another embodiment of the small bell of FIG. 2;

FIG. 10 is an isolated view of the lower portion of the small bell hopper of FIG. 1; and

FIG. 11 is a cross-sectional view of the lower portion of the small bell hopper taken at lines XI XI of FIG. 10.

DETAILED DESCRIPTION The blast furnace top charging device, generally indicated at 11 of FIG. 1, rests on top of a blast furnace 9. The top charging device 11 comprises, in FIG. 1, a chute 13, a small first bell chamber 15 with a cooperating small first frusto-coni cal bell 17, and a large second bell chamber 19 with a cooperating large second frusto-conical bell 21.

The chute 13 is the uppermost unit of the top charging device 11 and is adapted to receive materials from a skip car 23, a conveyor or the like. The skip car 23 is conventionally mounted to rails 25 on which the skip car 23 travels to carry successive loads of various ingredients to be charged into the blast furnace 9. The chute 13 is fixed to supporting structure 7 and is separated apart from the small first bell chamber 15 as indicated in FIG. 1. The remaining parts of the top charging device 11 are mounted to blast furnace 9.

The small chamber 15 has flap valves 27 at its top which are fully opened so that the raw materials from the skip car 23 pass through the chutes 13 into the small first bell chamber 15 and which are completely closed after the discharge of materials into the chamber 15. conventionally, two chutes 13 are placed opposite one another about the centerline of the fur nace with two cooperating flap valves 27 so that the bell rods 47 and the like may pass through the center of the furnace 9. The chute 13 and the flap valve 27 are conventional equipment well known to those skilled in the art.

The small first bell chamber 15 has a configuration as illustrated in FIG. 1 including a frusto-conical upper portion 15a and an inverted frusto-conical lower portion 15b. The lower portion 15b is made of two cooperating sections, a first section 16 and a second section 18 that are attachable and severable from each other. The first section 16 has at its lower end in FIG. a flange 37a extending outwardly of bell chamber and completely or intermittently surrounding the periphery of the first section, as desired. The second section 18, also, has a cooperating flange 37b at its upper peripheral edge extending outwardly of the bell chamber 15 for cooperating with flange 37a of the first-section 16. The cooperating flanges 37a and 37b have spaced apart apertures 38a and 38b through which bolts 40, fasteners or the like pass to hold the second section 18 firmly in place with the first section 16. Thus, in FIG. 5 the bell chamber 15 has an inverted frusto-conical supporting surface 39 defined by both sections 16 and 18.

The lower end of the second section 18 of the lower portion 15b is turned downwardly and flared outwardly of the bell chamber 15 to form a first sealing surface 41 that cooperates and engages the small bell 17 to maintain a gastight seal therebetween. To maintain the gastight seal and to extend the life of the supporting surface 39 and the first sealing surface 41, a layer of hard, abrasion-resistant material 43 covers these surfaces. The hard abrasion-resistant material 43 comprises parallel weld beads of about three-eighths inch in thickness, as desired. The composition of the hard abrasion-resistant material may be selected by those skilled in the art, as desired; however, the preferred composition is generally a chromium steel.

In the upper region of the small first bell chamber 15 in FIG. I a distributing means 29 is coaxially disposed therein for uniformly distributing the raw materials within the small first bell chamber 15 upon their discharge through the opened flap valves 27.

The small frusto-conical bell l7 completes the bottom of the small first bell chamber 15 by engaging the first seating surface 41 when the small bell 17 is in its closed position. The small first bell 17 is connected to a bell actuator 45 by means of bell rods 47 or the like which open and close or lower or raise the bell 17 in respect of the bell chamber 15 in FIG. 1.

The small bell 17 comprises a plurality of top and bottom sections. Herein the small bell 17 has two principal embodiments, one embodiment being for the initial installation of the top charging device as is illustrated in FIG. 9 and the other embodiment of the small bell 17 preferably being used as a replacement for the various parts of the small bell as illustrated in FIGS. 3.

In FIG. 9, illustrating the embodiment for the initial installation of the top charging device, the bell 17 has two top sections (A and B) and one bottom section (E), which, when placed together properly, provide a frusto-conical surface 49 as shown in FIGS. 2 and 4. The two top sections (A and B) are semicircular frusto-conical portions of the bell 17 and the bottom section (E) is a single, unitary, frusto-conical portion of the small bell 17. The bottom section (E) is made of two cast or fabricated semicircular parts.

In FIGS. 4, 5 and 9 each top section (A and B) includes a plurality of vertically arranged flanges 33 that have apertures 35 through which fasteners 36 or bolts shown in FIG. 5 pass for engagement with the corresponding flanges of the other top section. The two top sections (A and B) are thus held together by these bolts.

Each top section (A and B) includes at its lower end a first rim 53 that projects inwardly of the bell 17. The first rim 53 has a plurality of apertures 55 that are equally spaced apart.

In FIG. 9 the single bottom section (B) has its upper end a second rim 57 that likewise projects inwardly of the bell 17 with equally spaced apart apertures 57 for communicating with the apertures 55 of the first rim 53 of each top section (A and B). Fasteners or bolts 61 illustrated in FIG. 5 pass through these apertures 55 and 59 for holding the two top sections (A and B) to the single bottom section (E).

In the initial installation of the bell 17 of this invention, the respective top and bottom sections (A, B, and E) are assembled together as hereinbefore described before they are installed into the top charging device 11. Generally, the lower section (E) is subjected to more abrasion than the upper sections (A and B); when replacement of the lower section (E) is required, the lower section (E) is preferably replaced with two lower sections (C and D) as illustrated in FIG. 3. The two replacement parts of the lower section (C and D) are convenient in that the top charging device 11 need not be completely disassembled to replace new lower sections whereas using one single unit lower section would necessitate disassembling the top charging device 11.

In FIG. 3, illustrating the preferred embodiment of the bell for replacement of the bottom sections, the bell 17 has two top sections (A and B) and two bottom sections (C and D) which, when properly placed together, provide a frusto-conical surface 49 in FIG. 2. Each of the bottom sections (C and D) in FIG. 3 have at their upper ends a second rim 57 that projects inwardly of the bell 17, each having a plurality of spaced apart bores 59 for communicating with the bores 55 of the fust rim 53 of the top sections (A and B). A bolt 61 or the like passes through the respective, aligned bores 55 and 59 for holding the top section A and the bottom section C together and top section B and bottom section D together.

Each lower section (C and D) includes vertical flanges 33, similar to the vertical flanges of the upper section (A and B). The flanges 33 of the lower sections (A and B) have apertures 35 shown in FIG. 4 through which fasteners or bolts 36 shown in FIG. 5 pass for engagement with the corresponding flange of the other bottom section.

In the replacement of the initial lower section (E) of FIG. 9, bolts 61 are released and lower section (E) is removed while upper section (A and B) are still appended to bell levers 47. Two new lower sections (C and D) of FIG. 3 are installed, one at a time. The lower sections (C and D) are bolted together and then bolted to the respective upper sections (A and B).

In FIGS. 2 through 5 and FIGS. 3 and 10, illustrating the novel deflecting device of this invention, the bottom sections (C and D) or (E) of the bell 17 include a retaining shelf 63 or a ring that is mounted to and that completely surrounds the frusto-conical surface 49 of the bell 17. The ring 63 in FIG. 5 comprises a retaining surface 65 or an inner surface, an upper surface 67 and an outer surface 69 in FIG. 5. The retaining surface 65 projects upwardly from the frusto-conical surface 49 of the bell 17 at a certain angle to the frusto-conical surface, consequently forming a pocket 71 for retaining a small portion of ore and the like. In accordance with the invention, this angle may vary; however, in FIG. 4 the retaining surface lies in a cylindrical plane that is coaxial with the longitudinal axis A" of the bell 17. The height of the retaining surface 65 from the frusto-conical surface 49 of the bell 17 may be varied, as desired, provided that its height is sufficient to prevent any impingement of raw materials on the sealing surface of the bell. In FIG. 4, the upper surface 67 of the retaining shelf 63 lies in a plane that is normal to the longitudinal axis A ofthe bell 17.

Terminating at the lower periphery of the assembled bell 17 is a second seating or sealing surface 73 which is engageable and cooperative with the first seating surface 41 of the bell hopper 15. Together the first and second seating surfaces (41 and 73) provide a gastight seal between the bell 17 and the bell hopper 15. When raw materials are discharged from the bell hopper by the lowering of the bell 17 from the bell hopper, the raw material initially fills the pocket 71 and then in subsequent operation the raw material flows over the retained material and out of contact with the seating surfaces as shown in phantom lines in FIG. 4. Further, hot gases which eventually escape through the seating surfaces (41 and 73) will be channelled upwardly by surface 69 of ring 63 and surface 39 of the bell hopper which provide a diverging channel from the seating surfaces, to extend the service life of the bell 17.

For further protection the frusto-conical surface 49, the upper surface 67, the outer surface 69 of the ore retaining shelf 63 and, the second seating surface 73 are all covered with a hard abrasion resistant material 43 in a similar manner as hereinbefore described.

The supplemental sealing means, generally 81, is located at the lower edge of the bell hopper 17 immediately beneath the first sealing surface 41. The sealing means comprises an upper ring or circular upper plate 83, a matching lower ring or a matching circular lower plate 85 with two sealing gaskets (87 a, b) placed therebetween as shown in FIGS. 5. The upper plate 83 is connected by welding or the like to the second portion 18 of the bell hopper 15 around its periphery. Fasteners or bolts 89 urge the lower plate 85 and the upper plate 83 together.

The inner sealing gasket (87 a) is a circular gasket having a generally rectangular cross section; however, other types of gaskets may suitably be used with the invention.

In FIG. 5 the inner sealing gasket 87 a has a sealing face or sealing edge 87 c which is exposed for engagement with the second seating surface 73 of the bell 17. Thus, when the bell 17 is in its closed position in respect of the hopper 15 the sealing gasket 87 a engages the seating surface 73 thereby supplementing the metal to metal seal of the engaging seating surface 41 and 73 and extending the life of the bell and the hopper.

The outer sealing gasket 87 b serves as a spacer for preventing the bottom plate 85 from becoming biased in respect of the upper plate 83 when the bolt 89 urges the two plates (83, 85) together.

The sealing gaskets 87 a,b may be composed of any suitable material that withstands the high pressures and temperatures in operation of the top charging device 11. In this embodiment a gasket of a silicone material is used.

The lower plate 85 further includes retaining or retention plates (91 a,b) that extend upwardly for holding the sealing gaskets 87 a,b between the upper and lower plates.

In FIGS. 6 and 7, a recess 93 is provided at the joints 51 in the bell 17. The recess 93 is filled with a welding material 95 for sealing the joints. The material 95 does not extend beyond the frusto-conical surface 49 at the seating area. The hard abrasion-resistant material 43 is placed over and covers the frusto-conical surface 49 including the joints 51 in the embodiment of FIG. 9, thereby avoiding an exposed joint 51. Welding may also be provided on the upper sections, if desired. In FIG. 10 and 11 the joints of the lower section 18 of the bell hopper are similarly light seal welded.

In the replacement of the bottom section E of the bell 17 as hereinbefore described a worker uses conventional arc-air apparatus to burn through the abrasion-resistant surface 43 and to burn out the weld 95. When new bottom sections (C and D) are subsequently installed an exposed joint 51 exists. Thus in the case of the embodiment of FIG. 3 it is very desirable to use the supplemental sealing means 81 to protect the exposed joint from gases.

In FIG. 5 the lower section 18 of the small bell hopper 15 comprises two sections which may similarly be replaced. Bolts 40 are released and the second portion 18 is detached from the first 16 of the bell hopper. A worker then uses a conventional arc-air apparatus to burn through the abrasion-resistant surface 53 and the weld 95. Subsequently new lower sections 18 are installed.

Directly beneath the small first bell chamber 15, the large second bell chamber 19 is located in FIG. 1 on top of the furnace and is similarly connected integrally with the small first bell chamber 15 to retain the high pressure gasses therein. The large second frusto-conical bell 21 forms the bottom of the large second bell chamber 19 and is similarly connected to the actuator 45 by means of bell rods 47. The large bell 21 may similarly be provided with the improvements of this invention as shown in FIG. 1.

The method of replacing the sealing gaskets (87 a,b) is illustrated in FIG. 8. To replace the seal, temporary supports 101 are placed under the sealing means 81 and welded or bolted to the bell 17 as shown in FIG. 8. The bolts 89 are removed and the bell 17 is opened to its full stroke, whereby the lower plate 85 and the sealing gaskets 87 a,b are suspended on the temporary supports 101. New bolts 89' are used. A worker then removes the sealing gaskets 87 a,b and replaces new sealing gaskets to the lower plate 85. The bell 17 is raised to its closed position, the bolts 89' are replaced to secure the new sealing gaskets 87 a,b and the lower plate 85 to the upper plate 83 of the sealing means 81. The temporary supports 101 are then removed. The seal compression of the sealing gasket 87 a may be inspected before the bell is returned to normal operative service.

The foregoing devices and methods have been described in conjunction with the small bell 17 of the top charging device of FIG. 1 and optionally with the large bell 21. Further the invention may be incorporated with any conventional top charging devices for furnaces other than blast furnaces.

By the use of the retaining shelf 63 raw materials, when discharged from the bell hoppers, do not come in contact with the seating surfaces (41, 73) of the top charging device thereby extending the life of the bells. Further the sealing means 81 supplements and maintains a gastight seal between the bell and bell hoppers and by using the sealing means 81 of this invention the replacement of sealing gaskets (87 a,b) may be simply accomplished in accordance with the invention.

What is claimed is:

1. In a top charging device for a metallurgical furnace comprised of a bell hopper having an inverted frusto-conical surface that terminates in a first seating surface and comprised of a bell having a frusto-conical surface that terminates in a second seating surface at the lower peripheral edge of said bell; said first and second seating surfaces being capable of cooperating with each other to form a gastight seal wherein the improvements comprises:

a. a retaining surface that surrounds said frusto-conical surface and that projects upwardly from said frusto-conical surface at an angle relative to said frusto-conical surface to form a pocket for retaining a portion of raw materials; said retaining surface projecting from said frusto-conical surface such that said retaining surface clears said bell hopper as said bell is lowered from said bell hopper; and

b. a supplemental sealing means for assuring said gastight seal between said bell and said bell hopper comprising:

i. an upper circular plate mounted to the lower periphery of said bell hopper below said first seating surface,

thereof;

ii. a matching lower circular plate iii. a circular sealing gasket disposed between said upper and lower plates; said sealing gasket having a sealing edge exposed for engagement with said second seating surface of said bell; and

iv. fasteners for urging said upper and lower plates together.

2. The improvement of claim 1 wherein said bell hopper is comprised of a plurality of sections which when placed together define said inverted frusto-conical surface.

3. The improvement of claim 2 wherein said sections of said bell hopper are held together at joints that extend longitudinally of said bell hopper by fasteners; each of said sections being recessed at said joints; a welding composition substantially filling said recesses; and, a hard abrasion-resistant covering placed over said inverted frusto-conical surface of said bell hopper to protect said inverted frusto-conical surface and said joints from abrasion.

4. The improvement of claim 1 wherein said bell has a plurality of upper sections and at least one bottom section; and wherein said retaining surface is mounted to said bottom section.

5. The improvement of claim 1 wherein said bell has a plurality of upper sections and a plurality of bottom sections; said bottom sections being held together at joints that extend longitudinally of said bell by fasteners; each of said sections being recessed at said joints; a welding composition substantially filling said recesses; and a hard-abrasion-resistant covering placed over said frusto-conical surface of said bell to protect said frusto-conical surface and said joints from abrasion.

6. In a top charging device for a metallurgical furnace having a bell hopper with a first seating surface and a large bell with a frusto-conical surface that terminates in a matching second seating surface at the lower peripheral end of the conical surface; said first and second sealing surfaces cooperating with each other to form a gastight seal wherein the improvement comprises:

an upper circular plate mounted to the periphery of said bell hopper below said second seating surface thereof;

a matching lower circular plate;

a circular sealing gasket disposed between said upper and lower plates; said sealing gasket having a sealing edge exposed for engagement with said first seating surface of said bell for maintaining a gastight seal; and

fasteners for urging said upper and lower plates together.

7. The improvement of claim 6 further comprising:

a spacer that is disposed between said upper and lower plates and that is adjacently disposed with said sealing gasket for preventing said upper and lower plates from being biased in respect of each other as said fasteners urge said plates together.

8. The improvement of claim 7 wherein said spacer comprises a circular sealing gasket.

9. The improvement of claim 8 further comprising:

retention plates disposed between said upper and lower plates near the edges thereof for holding said sealing gaskets between said upper and lower plates. 

1. In a top charging device for a metallurgical furnace comprised of a bell hopper having an inverted frusto-conical surface that terminates in a first seating surface and comprised of a bell having a frusto-conical surface that terminates in a second seating surface at the lower peripheral edge of said bell; said first and second seating surfaces being capable of cooperating with each other to form a gastight seal wherein the improvements comprises: a. a retaining surface that surrounds said frusto-conical surface and that projects upwardly from said frusto-conical surface at an angle relative to said frusto-conical surface to form a pocket for retaining a portion of raw materials; said retaining surface projecting from said frusto-conical surface such that said retaining surface clears said bell hopper as said bell is lowered from said bell hopper; and b. a supplemental sealing means for assuring said gastight seal between said bell and said bell hopper comprising: i. an upper circular plate mounted to the lower periphery of said bell hopper below said first seating surface, thereof; ii. a matching lower circular plate iii. a circular sealing gasket disposed between said upper and lower plates; said sealing gasket having a sealing edge exposed for engagement with said second seating surface of said bell; and iv. fasteners for urging said upper and lower plates together.
 2. The improvement of claim 1 wherein said bell hopper is comprised of a plurality of sections which when placed together define said inverted frusto-conical surface.
 3. The improvement of claim 2 wherein said sections of said bell hopper are held together at joints that extend longitudinally of said bell hopper by fasteners; each of said sections being recessed at said joints; a welding composition substantially filling said recesses; and, a hard abrasion-resistant covering placed over said inverted frusto-conical surface of said bell hopper to protect said inverted frusto-conical surface and said joints from abrasion.
 4. The improvement of claim 1 wherein said bell has a plurality of upper sections and at least one bottom section; and wherein said retaining surface is mounted to said bottom section.
 5. The improvement of claim 1 wherein said bell has a plurality of upper sections and a plurality of bottom sections; said bottom sections being held together at joints that extend longitudinally of said bell by fasteners; each of said sections being recessed at said joints; a welding composition substantially filling said recesses; and a hard-abrasion-resistant covering placed over said frusto-conical surface of said bell to protect said frusto-conical surface and said joints from abrasion.
 6. In a top charging device for a metallurgical furnace having a bell hopper with a first seating surface and a large bell with a frusto-conical surface that terminates in a matching second seating surface at the lower peripheral end of the conical surface; said first and second sealing surfaces cooperating with each other to form a gastight seal wherein the improvement comprises: an upper circular plate mounted to the periphery of said bell hopper below said second seating surface thereof; a matching lower circular plate; a circular sealing gasket disposed between said upper and lower plates; said sealing gasket having a sealing edge exposed for engagement with said first seating surface of said bell for maintaining a gastight seal; and fasteners for urging said upper and lower plates together.
 7. The improvement of claim 6 further comprising: a spacer that is disposed between said upper and lower plates and that is adjacently disposed with said sealing gasket for preventing said upper and lower plates from being biased in respect of each other as said fasteners urge said plates together.
 8. The improvement of claim 7 wherein said spacer comprises a circular sealing gasket.
 9. The improvement of claim 8 further comprising: retention plates disposed between said upper and lower plates near the edges thereof for holding said sealing gaskets between said upper and lower plates. 